Prenatal Exposure to Inflammation Decreases Endothelial Cell Proliferation in the Mouse Intestinal Mucosa

Abstract

Necrotizing enterocolitis (NEC) is the most devastating gastrointestinal disease affecting premature infants. Chorioamnionitis has been shown to increase its incidence. However, the mechanism by which prenatal infection increases susceptibility to NEC remains elusive. Our lab has shown that VEGF is decreased in human NEC. VEGF may play a role in NEC pathogenesis by compromising vascular network integrity. Here we hypothesized that antenatal inflammation decreases the expression of vascular endothelial growth factor (VEGF) in intestine tissues and mucosal vascular endothelial cell proliferation. To test our hypothesis, pregnant mice were injected i.p. at E16 with LPS or normal saline. VEGF protein of Day 0 pup intestines was analyzed by western blot and band density values normalized to b‐actin. To quantify endothelial cell (E.C.) proliferation, pups were injected with BrdU i.p. 4 hours prior to euthanasia, and the number of BrdU positive cells co‐staining for CD31, an endothelial cell marker, were counted in the villi (3 fields/ sample at 10x magnification). We found that intestinal VEGF expression was significantly lower in pups from LPS‐treated dams compared to controls (mean±SEM: 1.40 ± 0.14 v.s 2.80 ± 0.15; p<0.0005). Also, the number of proliferating endothelial cells was significantly decreased in newborn pups from LPS‐treated dams compared to controls (8.0 ± 0.88 v.s 26.0 ± 1.60; p<0.0001). In conclusion, prenatal exposure to inflammation decreases intestinal VEGF protein and intestinal mucosal endothelial cell proliferation. This suggests that antenatal inflammation may predispose to intestinal injury and NEC by affecting mucosal microvasculature (supported by NIH grant RO1HD060876).